1. Field of the Invention
The present invention relates to an image recording technique and in particular to a technique for recording an image by using a conductive ink.
2. Description of the Related Art
An inkjet full-line color printer is known as an image recording apparatus for recording an image on a recording medium such as paper. A full-line color printer is equipped with the nozzle array recording heads of respective colors separated from one another in predetermined intervals in the direction of conveying a recording medium, that is, the feed direction thereof. A plurality of nozzles for jetting ink are arrayed in each of the nozzle arrays so as to be formed across a length which is no less than the width of a recording medium in a direction orthogonal to the aforementioned feed direction, that is, the cross-feed direction.
Such an image recording apparatus, that is, a color printer, is equipped with its nozzle arrays facing the recording medium, so that a desired character and/or image are recorded by jetting ink onto the recording medium from the plurality of nozzles equipped in the individual nozzle arrays of respective colors.
A technique related to such a nozzle array (i.e., a recording head) is disclosed by the inkjet head noted in, for example, registered Japanese Patent No. 3506356. This reference patent document has disclosed a configuration in which ink chambers are equipped parallelly by forming a large number of channels on a base plate made from a piezoelectric transducer (PZT), with an electrode being formed on the internal surfaces of the respective ink chambers. In the inkjet head, the volume of the individual ink chamber is changed by applying a voltage to the electrode and thereby the ink is jetted.
The aforementioned reference patent document has also disclosed the manufacturing technique of the inkjet head. In this manufacturing technique, a first channel (i.e., an ink chamber) and a second channel are formed by processing a base plate, i.e., the PZT, and a discrete electrode and a common electrode are formed on the aforementioned base plate. The patent document further describes a configuration example of a conventional inkjet head. The inkjet head comprises an ink chamber formed by a side wall partly consisting of a piezoelectric transducer (PZT), an interval (or space) equipped between individual ink chambers, a discrete electrode, a common electrode, and a nozzle plate forming a nozzle (i.e., an inkjet nozzle) communicating with each respective ink chamber.
In the meantime, the demand for an aqueous ink in place of the conventional pigment ink as the ink used for an image recording apparatus has been increasing in recent years in consideration of environmental problems and such.
FIG. 1 is a cross-sectional diagram illustrating the structure of a conventional recording head premising the use of a conductive ink.
Referring to FIG. 1, in a recording head 43, a base plate 45 forms ink chambers 37, that is, a plurality of channels, with an interval 41 being equipped between individual ink chambers 37. A side wall made from a piezoelectric transducer (PZT) is formed on either side of the ink chamber 37, separating the ink chamber 37 from the interval 41. A nozzle plate 38 forming a nozzle 38a is equipped below the ink chamber 37. Note that the nozzle plate 38 is equipped so that the ink within the ink chamber 37 is conduced to the nozzle 38a. 
Further, a discrete electrode 42 is equipped on the side wall 44 toward the ink chamber 37, with an insulation film 40 covering the discrete electrode 42. Further, a drive cable is connected to the discrete electrode 42 so that a drive signal generated by a drive circuit 39 is given to the discrete electrode 42.
Further, a common electrode 46 is equipped on the side wall 44 near the interval 41. A common cable is connected to the common electrode 46, which is conductive to, for example, the ground (GND) (i.e., zero volts) of the drive circuit 39.
Thusly configured individual ink chambers 37 of the recording head 43 store respective conductive inks 37a supplied from ink supply systems. In this event, the drive circuit 39 providing a potential difference (i.e., a drive signal) between the discrete electrode 42 and common electrode 46 causes the side wall 44 made from the piezoelectric transducer (PZT) to deform and accordingly the volume of the ink chamber 37 to change. Then the conductive inks 37a stored in the ink chambers 37 are jetted out of the nozzle 38a. 
Next is a description of the operation of an image recording apparatus when it receives job information required for recording an image and starts an image recording.
In this event, having received the job information from a host apparatus, the image recording apparatus sometimes performs the process for moving a conveyance mechanism that supports and conveys a recording medium at the position opposite to the nozzle array to the recording process (i.e., the image recording) position by driving, for example, a conveyance mechanism elevation unit. The reason for this is that, when the image recording apparatus is left without, for example, any recording process being carried out, the image recording apparatus performs the process for retracting the conveyance mechanism below the nozzle array and making a droplet reception unit receive ink droplets dropping from the nozzle of the nozzle array.
Therefore, the image recording apparatus performs a recording process in the process of the conveyance mechanism supporting and conveying the recording medium conveyed from the upstream area of the conveyance path of the recording medium after completing the process for moving the conveyance mechanism to the recording process position.
Note that such a conveyance mechanism is generally earth-grounded to the frame of the image recording apparatus.
Meanwhile, it is generally known that an image recording apparatus carries out a recovery process in order to prevent an increase in the viscosity of the ink within the nozzle and a consequent clogging of the inkjet hole.
The recovery mechanism of the image recording apparatus comprises a reception unit for receiving an ejected ink droplet and a wiping unit for wiping ink that has dripped from a nozzle in order to prevent ink contamination within the apparatus.
Note that such a recovery mechanism is generally grounded to the frame of the image recording apparatus.